Component carrier tape

ABSTRACT

A flexible carrier tape for storage and delivery of components by an advancement mechanism, comprises a strip portion, a plurality of aligned pockets spaced along the strip portion for carrying the components, wherein each pocket includes a bottom wall, and a non-pressure sensitive adhesive comprising a thermoplastic elastomer block copolymer on the bottom wall of the pocket for retaining a component in the pocket.

BACKGROUND OF THE INVENTION

1. Technical Field

This invention relates generally to carrier tapes of the kind used totransport components from a component manufacturer to a differentmanufacturer that assembles the components into new products. Morespecifically, this invention relates to carrier tapes for storingelectronic surface mount components and for supplying those componentsseriatim to a machine.

2. Description of the Related Art

In general, carrier tapes that are used to transport components from acomponent manufacturer to a different manufacturer that assembles thecomponents into new products are well known. For example, in the fieldof electronic circuit assembly, electronic components are often carriedfrom a supply of such components to a specific location on a circuitboard for attachment thereto. The components may be of several differenttypes, including surface mount components. Particular examples includememory chips, integrated circuit chips, resistors, connectors, dualin-line processors, capacitors, gate arrays, etc. Such components aretypically affixed to a circuit board that may later be incorporated intoan electronic device.

Rather than manually affixing each individual electronic component to acircuit board, the electronics industry makes extensive use of roboticplacement machines, sometimes known as "pick-and-place" machines, whichgrasp a component at a specific location (the supply) and place it atanother specific location (the circuit board). To ensure the sustainedoperation of the robotic placement machine, a continuous supply ofelectronic components must be furnished to the machine at apredetermined rate and location to permit the machine to be programmedto repeat a precise sequence of movements during every cycle. It istherefore important that each such component be located in the sameposition (i.e. the point at which the robotic placement machine graspsthe component) as each preceding and succeeding component.

One way to provide a continuous supply of electronic components to adesired location is to use a carrier tape. Conventional carrier tapesgenerally comprise an elongated strip that has a series of identicalpockets formed at predetermined, uniformly spaced intervals along thelength of the tape. The pockets are designed to receive an electroniccomponent. A continuous cover tape is applied over the elongated stripto retain the components in the pockets. The tapes also normally includea series of through holes uniformly spaced along one or both edges ofthe elongated strip. The through holes receive the teeth of a drivesprocket that advances the tape toward the robotic placement machine.

Each pocket is shaped to closely receive the electronic component.Frequently, the pockets are sized to match a particular component. Infact, the tolerances between the component and the pocket walls may bequite small such that a given carrier tape may only be useful with asingle size of component. Thus, a component of a different size wouldrequire a new pocket design. In conventional carrier tapes, if thepockets are not properly sized for the stored component, the componentmay rotate within the pocket making subsequent removal by automaticpick-up equipment difficult or impossible since these devices requireprecise component orientation for proper removal. A component may eventurn over within its pocket during shipping, necessitating reorientationof the stored component. Excessive component movement may also result ina component becoming damaged as it collides with the pocket walls. Giventhese variables, it can be expensive to design, manufacture and store amultitude of different carrier tapes having different pocket designs fordifferent components.

Eventually, the carrier tape is fed to a robotic placement machine thatstrips the continuous cover tape from the carrier and removes thecomponents from the pockets and places them onto the circuit board.Removal of the component is commonly accomplished with a vacuum pick-updevice that grasps the top of the component by suction. The vacuumpick-up may be assisted by a push-up needle or probe that penetrates ahole formed in the floor of the pocket to push up against the component.The removed cover tape is waste that must be gathered and disposed.

U.S. Pat. No. 4,778,326 (Althouse et at.) discloses a carrier that isadapted for handling semiconductor chips and other smooth-surfacedarticles. The carrier includes a base that has a recess within itsinterior. The recess includes a plurality of protuberances that supporta thin flexible film cover that overlies the base. Semiconductor chipsare carded on the upper surface of the cover. By connecting the base toa vacuum, the cover can be drawn down into the base recess and againstthe protrusions. This converts the cover from a flat condition in fullsurface contact with the semiconductor chip to a wavy or undulatingcondition having reduced surface contact with the semiconductor chip.Reportedly, the reduced surface area contact facilitates removal of thesemiconductor chip.

However, Althouse et al. note that while their invention is adapted foruse with a wide variety of chip sizes, the number and the size of theprotuberances employed in the base are selected in relationship to thesize of the chips to be handled. As a result, a chip which is too smallfor proper use with the carrier could be drawn down with the cover intoa recess and its removal from the carrier would not be facilitated.

U.S. Pat. No. 4,667,944 (Althouse) discloses a related device in which atextured fabric is sandwiched between the cover and the base. Tofacilitate removing the semiconductor chip from the cover, surfacecontact between the cover and the chip is reduced by drawing portions ofthe cover into crevices in the upper face of the textured fabric byapplying a vacuum thereto.

Although the invention is apparently adapted for use with a wide varietyof chip sizes, Althouse notes that among the factors to be considered inselecting the textured fabric is the size of the devices to be handled.

U.S. Pat. No. 5,089,314 (Masujima et al.) discloses a carrier tape forsurface mounted electronic circuit elements which includes a tape bodyhaving an adhesive applied thereto. The adhesive is formed of a materialthat does not exhibit any adhesion at a normal temperature but whichdoes exhibit adhesion when heated to a temperature of about 80° C. Theadhesive may be a silicone, an acrylic resin, or a mixture of siliconeand acrylic resin. When the electronic circuit element is removed fromthe carrier, the adhesive transfers to the bottom of the circuitelement. The circuit element and the adhesive are then heated such thatthe adhesive can provisionally bond the circuit element to a printedcircuit board.

U.S. Pat. No. 4,966,281 to Kawanishi et al. discloses an electroniccomponent carrier having a series of electronic component-mountingportions that include a layer of adhesive. The adhesive is a rubbertype, an acryl type or a silicone type having suitable pressuresensitive adhesive properties. The use of a push bar enables smoothremoval of the electronic component from the adhesive layer.

However, there is still a need for a carrier tape that can securelyretain a stored component in the proper orientation for subsequentremoval by an automated device. It would be highly desirable if thiscould be accomplished without the need for separate carrier tapes fordifferent component sizes and designs. It would also be highly desirableif this could be accomplished without using a cover tape. Such carriertapes would offer even further advantages if any adhesive used to retainthe components on the carrier tape did not display pressure sensitiveadhesive properties because tacky pressure sensitive adhesives canretain dirt and other potential contaminants. Similarly, it would beuseful if the adhesive did not transfer to the stored component uponremoval of the component so as to reduce the risk of contamination.

SUMMARY OF THE INVENTION

In one embodiment, the invention relates to a flexible carrier tape forstorage and delivery of components by an advancement mechanism. Thecarrier tape comprises a strip portion having a top surface, a bottomsurface opposite the top surface, a plurality of aligned pockets forcarrying the components, the pockets being spaced along the stripportion and opening through the top surface thereof. The pockets includeat least one side wall that adjoins and extends downwardly from thestrip portion, and a bottom wall that adjoins the side wall. The pocketsmore preferably include four side walls each at generally fight angleswith respect to each adjacent side wall. Typically, each of the pocketsis essentially identical and are equally spaced along the strip portion.The bottom wall of each pocket may include an aperture or through holeto, for example, accommodate a mechanical push-up. The strip portionfurther has first and second parallel longitudinal edge surfaces, andpreferably at least one of the edge surfaces includes a plurality ofequally spaced holes for receiving the advancement mechanism.

The bottom wall of the pocket includes a non-pressure sensitive adhesivefor retaining the component in the pocket. The adhesive inherentlydisplays sufficient adhesion to the component at room temperature toretain the component in the pocket. The adhesive comprises athermoplastic elastomer block copolymer and preferably has a storagemodulus greater than 1×10⁶ Pascals at room temperature. Thethermoplastic elastomer block copolymer may comprise segments of styreneand segments of a rubbery elastomer. Specific examples of thermoplasticelastomer block copolymers useful in the invention includestyrene-ethylene/propylene-styrene block copolymer,styrene-ethylene/propylene-styrene-ethylene/propylene block copolymer,styrene-ethylene/butylene-styrene block copolymer, and blends thereof.

Advantageously, the adhesive may exhibit a peel adhesion of about 20 to200 grams per linear inch width to the stored component (morepreferably, a peel adhesion of about 50 to 140 grams per linear inchwidth) and can maintain this adhesion even after dwelling in contactwith the component for a period of at least 7 days under ambientconditions. However, upon removal of the component from the pocket, theadhesive desirably does not transfer to the component.

Optionally, the adhesive may include an adhesion modifier to achieve thedesired level of adhesion. The adhesion modifier may be a tackifyingresin (which typically is present in an amount of less than 10% byweight, based on the combined weight of the thermoplastic elastomerblock copolymer and tackifying resin), a liquid rubber (which typicallyis present in an amount of less than 20% by weight based on the combinedweight of the thermoplastic elastomer block copolymer and the liquidrubber), or a photocrosslinking agent.

The carrier tape can optionally include a cover that is releasablysecured to the top surface of the strip portion, extends along the stripportion, and covers the pockets. Advantageously, however, the carriertapes of the invention do not require a cover.

The carrier tapes of the invention are especially useful for storing anddelivering surface mount electronic components to a machine, such as arobotic placement machine. To facilitate this, the carrier tape can bewound about a core to form a supply reel.

Since the adhesive provides the means for securely retaining thecomponent in the pocket, a single pocket having a generic design may beused to accomodate components of widely varying shape and size.Consequently, the pockets need not be shaped to closely receive thecomponent nor must the pockets be sized to match a particular component.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be more fully appreciated with reference to thefollowing drawings in which similar reference numerals designate like oranalogous components throughout and in which:

FIG. 1 is a fragmentary perspective view of one embodiment of a carriertape according to the invention with an optional cover thereof havingbeen partially removed to show components stored within the carriertape, although the component has been omitted from the leading pocket inorder to show the interior of the pocket more clearly;

FIG. 2 is a sectional view taken along lines 2--2 in FIG. 1;

FIG. 3 is a plan view showing another embodiment of a carrier tapeaccording to the invention;

FIG. 4 is a plan view similar to FIG. 3 and showing a further embodimentof the invention;

FIG. 5 is a schematic illustration of one method for manufacturing acarrier tape according to the invention;

FIG. 6 is a schematic view illustrating how a carrier tape according tothe invention may be loaded with components followed by the applicationof an optional cover; and

FIG. 7 is a schematic view illustrating a robotic machine removingcomponents from a carrier tape according to the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Turning now to the drawings, one embodiment of a carrier tape accordingto the invention is shown in FIGS. 1 and 2. The illustrated carrier tapeis useful for the storage and delivery of components (especiallyelectronic components) by an advancement mechanism. More specifically, aunitary flexible carrier tape 100 has a strip portion 102 defining a topsurface and a bottom surface opposite the top surface. Strip portion 102includes longitudinal edge surfaces 104 and 106, and a row of alignedadvancement holes 108 and 110 formed in and extending along one, andpreferably both, edge surfaces. Advancement holes 108 and 110 provide ameans for receiving an advancement mechanism such as the teeth of asprocket drive for advancing carrier tape 100 toward a predeterminedlocation.

A series of pockets 112 is formed in and spaced along strip portion 102,the pockets opening through the top surface of the strip portion. Withina given carrier tape, each pocket is usually essentially identical tothe other pockets. Typically, they are aligned with each other andequally spaced apart. In the illustrated embodiment, each pocketincludes four side walls 114, each at generally fight angles withrespect to each adjacent wall. Side walls 114 adjoin and extenddownwardly from the top surface of the strip portion and adjoin bottomwall 116 to form pocket 112. Bottom wall 116 is generally planar andparallel to the plane of strip portion 102. Optionally, thoughdesirably, bottom wall 116 may include an aperture or through hole 117that is of a size to accommodate a mechanical push-up (e.g., a poke-upneedle) to facilitate removal of component 118 (such as an electroniccomponent) that is stored in pocket 112. Aperture 117 may also be usedby an optical scanner to detect the presence or absence of a componentwithin any given pocket. In addition, aperture 117 may be useful inapplying a vacuum to the pocket to permit more efficient loading of thepockets with components. A ring of adhesive 119 circumscribes aperture117 in the leading pocket and is discussed more fully hereinbelow.

Pockets 112 may be designed to conform to the size and shape of thecomponents that they are intended to receive although as discussed morefully below, one of the advantages afforded by the present invention isthat a single pocket of generic design may readily accommodatecomponents of widely varying size and shape. Although not specificallyillustrated, the pockets may have more or less side walls than the fourthat are shown in the preferred embodiment. In general, each pocketincludes at least one side wall that adjoins and extends downwardly fromstrip portion 102, and a bottom wall that adjoins the side wall to formthe pocket. Thus, the pockets may be circular, oval, triangular,pentagonal, or have other shapes in outline. Each side wall may also beformed with a slight draft (i.e., a 2° to 12° slant toward the center ofthe pocket) in order to facilitate insertion of the component, and toassist in releasing the pocket from a mold or forming die duringfabrication of the carrier tape. The depth of the pocket can also varydepending on the component that the pocket is intended to receive. Inaddition, the interior of the pocket may be formed with ledges, ribs,pedestals, bars, rails, appurtenances, and other similar structuralfeatures to better accommodate or support particular components.Although a single column of pockets is illustrated in the drawings, twoor more columns of aligned pockets could also be formed along the lengthof the strip portion in order to facilitate the simultaneous delivery ofmultiple components. It is expected that the columns of pockets would bearranged parallel to each other with pockets in one column being inaligned rows with the pockets in the adjacent column(s).

Strip portion 102 may be formed of any polymeric material that has asufficient gauge and flexibility to permit it to be wound about the hubof a storage reel. A variety of polymeric materials may be usedincluding, but not limited to, polyester (e.g., glycol-modifiedpolyethylene terephthalate), polycarbonate, polypropylene, polystyrene,polyvinyl chloride, and acrylonitrile-butadiene-styrene. Strip portion102 may be optically clear, pigmented or modified to be electricallydissipative. In the latter case, the strip may include an electricallyconductive material, such as carbon black or vanadium pentoxide, that iseither interspersed within the polymeric material or is subsequentlycoated onto the strip. The electrically conductive material allows anelectric charge to dissipate throughout the carrier tape and preferablyto the ground. This feature may prevent damage to components containedwithin the carrier tape due to an accumulated static electric charge.

Carrier tape 100 may optionally include an elongate cover 120, althoughas explained more fully below, one of the advantages afforded by thepresent invention is that a cover tape is not required. Cover 120 isapplied over the pockets of the carrier tape to provide an additionalway of retaining the components therein. Cover 120 can also protect thecomponents from dirt and other contaminants that could invade thepockets. As best shown in FIGS. 1 and 2, cover 120 is flexible, overliespart or all of pockets 112, and is disposed between the rows ofadvancement holes 108 and 110 along the length of strip portion 102.Cover 120 is releasably secured to the top surface of strip portion 102so that it can be subsequently removed to access the stored components.As illustrated, cover 120 includes parallel longitudinal bondingportions 122 and 124 that are bonded to longitudinal edge surfaces 104and 106, respectively, of strip portion 102. For example, a pressuresensitive adhesive such as an acrylate material, or a heat-activatedadhesive such as an ethylene vinyl acetate copolymer, may be used toadhere the cover to edge surfaces 104 and 106. Alternatively, cover 120could be secured to strip portion 102 by a mechanical fastener such as asnap fit interference fastener or a hook and loop fastener (with thehooks being carried by either the cover or the strip portion and theloops being carried by the other).

As noted above, bottom wall 116 of pocket 112 includes a ring ofadhesive 119 that circumscribes aperture 117. Adhesive 119 provides ameans for securely retaining component 118 in the pocket. As a result, asingle pocket having a generic design may be used to accomodatecomponents of widely varying shape and size since adhesive 119 providesthe principle means for retaining the component in the pocket.Consequently, pockets 112 need not be shaped to closely receive thecomponent nor must the pockets be sized to match a particular component.The tolerances between the component and the pocket walls may be quiteliberal. Moreover, cover 120 is not required to retain a component inthe pocket and its elimination facilitates handling the storedcomponents since waste otherwise generated by removing the cover doesnot have to be gathered and disposed.

While FIG. 1 shows adhesive 119 as a ring circumscribing aperture 117,neither the shape nor the placement of the adhesive is critical. Thus,as shown in FIG. 3, adhesive 119 may assume a half-ring or crescentshape, while the embodiment illustrated in FIG. 4 comprises a series ofround, spaced apart dots of adhesive distributed in a circular arrayabout aperture 117. The dots of adhesive may have other shapes (such assquares, triangles, etc.) and may be arranged in other than a circulararray (such as a square or triangular distribution). The illustratedembodiments show the adhesive centered with respect to aperture 117.While this is preferred, the adhesive may be positioned anywhere on thebottom wall of the pocket so long as the stored component can be removedtherefrom.

The amount of adhesive employed may vary over a wide range and will beinfluenced to a significant degree by the size of the component to becarried by the tape, larger components requiting a larger amount ofadhesive. In general the amount of adhesive that is used is sufficientto securely retain the component in the pocket in a readily retrievableorientation (flat is preferred) but without creating an adhesion levelthat is so high that the component cannot be removed by conventionalrobotic pick and place machines. A desired level of adhesion ispreferably about 20 to 200 grams per linear inch width (gliw), morepreferably about 40 to 150 gliw, and most preferably about 100 gliw,although the actual adhesion can depend on the size of the component,smaller components often requiring greater peel adhesion. The desiredadhesion values refer to peel adhesion as measured on a conventionaladhesion tester such as an Instrumentors, Inc. Slip-Peel Tester ModelSP-102C-3M90 adhesion tester using a peel angle of 180° and a rate of 30cm/min.

Adhesive compositions useful in the invention are non-pressure sensitiveadhesive (non-PSA) materials that comprise and, more preferably, consistessentially of a thermoplastic elastomer block copolymer. By a "non-PSA"is meant an adhesive that does not display pressure sensitiveproperties. A pressure sensitive adhesive is conventionally understoodto refer to an adhesive that displays permanent and aggressive tackinessto a wide variety of substrates after applying only light pressure. Anaccepted quantitative description of a pressure sensitive adhesive isgiven by the Dahlquist criterion line, which indicates that materialshaving a storage modulus (G') of less than about 3×10⁵ Pascals (measuredat 10 radians/second at room temperature, about 20° to 22° C.) havepressure sensitive adhesive properties while materials having a G' inexcess of this value do not. Thus, more specifically, a non-PSA, as usedherein, refers to a material that has a storage modulus at least abovethe Dahlquist criterion line, and more preferably, a storage modulusabove 1×10⁶ Pascals.

By a "thermoplastic elastomer block copolymer" is meant a copolymer ofsegmented A and B blocks or segments and which displays boththermoplastic and elastomeric (i.e., rubbery) behavior. For simplicity,the expressions "thermoplastic elastomer" and "block copolymer" aresometimes used herein to refer to a thermoplastic elastomer blockcopolymer. Thus, a thermoplastic elastomer may be readily distinguishedfrom natural and synthetic rubbers as well as conventionalthermoplastics (e.g., acrylates and vinyls). Thermoplastic elastomersuseful in the invention include multi-block copolymers having radial,linear A-B diblock, and linear A-B-A triblock structures, as well asblends of these materials. In these structures A represents anon-rubbery thermoplastic segment (e.g., an end block) and B representsa rubbery elastomeric segment (e.g., a midblock). However, smallproportions of other monomers may enter into the block copolymers.

Illustrative thermoplastic A blocks include mono- and polycyclicaromatic hydrocarbons, and more particularly, mono- and polycyclicarenes. Illustrative mono and polycyclic arenes include substituted andunsubstituted poly(vinyl)arenes of monocyclic and bicyclic structure.Preferred thermoplastic elastomers include thermoplastic segments ofsubstituted or unsubstituted monocyclic arenes of sufficient segmentmolecular weight to assure phase separation at room temperature. Thethermoplastic A blocks may comprise a homopolymer or copolymer ofalkenyl arenes.

The alkenyl arenes in the thermoplastic A blocks are preferablymonoalkenyl arenes. The term "monoalkenyl arene" will be taken toinclude particularly those of the benzene series such as styrene and itsanalogs and homologs including o-methylstyrene, p-methylstyrene,p-tertbutylstyrene, 1,3-dimethylstyrene, alpha-methylstyrene and otherring alkylated styrenes, particularly ring-methylated styrenes, andother mono-alkenyl polycyclic aromatic compounds such as vinylnaphthalene, vinyl anthracene and the like. The preferred monoalkenylarenes are monovinyl monocyclic arenes such as styrene andalpha-methylstyrene, and styrerie is particularly preferred.

The individual thermoplastic A blocks preferably have a number averagemolecular weight of at least about 6,000 so as to promote good domainformation and, more preferably, a number average molecular weight ofabout 8,000 to 30,000. The thermoplastic A blocks typically constituteabout 5 to 30 percent, and preferably, about 8 to 25 percent by weightof the block copolymer. When the B blocks are comprised of a saturatedrubbery elastomer segment, the most preferred thermoplastic elastomerscontain A blocks constituting about 15 to 25% by weight of the blockcopolymer.

The A-B-A designation includes block copolymers that are branched aswell as linear and also includes structures in which the end blocks aredifferent from one another but are both derived from styrene or styrenehomologs (such structures sometimes being known as A-B-C blockcopolymers).

The preferred rubbery elastomer B segments are polymer blocks composedof homopolymers of a monomer or copolymers of two or more aliphaticconjugated diene monomers. The conjugated dienes are preferably onescontaining from 4 to 8 carbon atoms. Examples of suitable conjugateddiene monomers include: 1,3-butadiene (butadiene),2-methyl-1,3-butadiene (isoprene), 2,3-dimethyl-1,3-butadiene,1,3-pentadiene (piperylene), 1,3-hexadiene, and the like.

In the most preferred styrenic block copolymers, the rubbery segmentsmay be saturated by hydrogenation of unsaturated precursors such as astyrene-butadiene-styrene block copolymer having center blockscomprising a mixture of 1,4 and 1,2 isomers. Upon hydrogenation of thelatter, a styrene-ethylene/butylene-styrene block copolymer is obtained.Similarly, a styrene-isoprene-styrene block copolymer precursor may behydrogenated to yield a styrene-ethylene/propylene-styrene blockcopolymer. Rubbery mateddais such as polyisoprene, polybutadiene andstyrene-butadiene rubbers may also be used to form the rubbery elastomersegments. Also particularly preferred are butadiene and isoprene.Mixtures of different conjugated dienes may be used too. The numberaverage molecular weight of the B blocks for the linear diblock andtriblock copolymers is preferably in the range of about 4,500 to180,000.

Radial block copolymers useful in this invention are of the typedescribed in U.S. Pat. No. 3,281,383 and conform to the followinggeneral formula: (A-B)nX, wherein A is a thermoplastic block polymerizedfrom styrene or styrene homologs, B is a rubbery elastomeddc blockderived from conjugated dienes, as indicated above, X is an organic orinorganic connecting molecule with a functionality of 2-4 such assilicon tetrachloride, tin tetrachloride, or divinyl benzene, althoughothers are mentioned in U.S. Pat. No. 3,281,383. X may have a higherfunctionality in which event "n" is a number corresponding to thefunctionality of X. The number average molecular weight of the radialblock copolymers is preferably in the range of about 125,000 to 400,000.

The thermoplastic elastomer may also comprise a mixture of radial orlinear triblock copolymers and simple diblock copolymers. However, theproportion of the diblock copolymers in the mixture of the triblock anddiblock copolymers should not exceed about 85 percent by weight andnormally lower percentages such as 30% would be used.

A wide variety of commercially available thermoplastic elastomers may beused (either alone or in combination) in the invention including theSOLPRENE family of materials (Phillips Petroleum Co.), the FINAPRENEfamily of materials (Fina), the TUFPRENE and ASAPRENE families ofmaterials (Asahi), the STEREON family of materials (Firestone SyntheticRubber & Latex Co.), the EUROPRENE SOL T family of materials Clinichem),the VECTOR family of materials (Dexco Polymers), and the CARIFLEX TRfamily of materials (Shell Chemical Co.). Also useful is the SEPTONfamily of materials (Kuraray Co. Ltd.), such as SEPTON 2002, 2005, 2007,2023, 2043 and 2063. Also useful is the KRATON family of materials(Shell Chemical Co.), such as D-1101, D-1102, D-1107P, D-1111, D-1112,D-1114PX, D-1116, D-1117P, D-1118X, D-1119, D-1122X, D-1124, D-1125PX,D-1184, D-1300X, D-1320X, 4141, 4158, 4433, RP-6408, RP-6409, RP-6614,RP-6906, RP-6912, G-1650, G-1651, G-1652, G-1654X, G-1657, G-1701X,G-1702X, G-1726X, G-1750X, G-1765X, FG-1901X, FG-1921X, FG-1924, andTKG-101. In general, the KRATON series of hydrogenated thermoplasticelastomers is preferred.

A class of materials which is highly preferred are hydrogenated blockcopolymers comprising segments of styrene and segments ofethylene/propylene, especially those which have reported couplingefficiency of 100%, have about 15 to 25% (even more preferably about 18to 23%) styrene, a tensile strength of about 3100 psi, and about a 9%set at break. Such materials may exhibit the following storage modulusprofile (at 10 radians/second): about 2.5×10⁶ to 4.0×10⁶ Pascals at 0°C., about 2.7×10⁶ to 4.0×10⁶ Pascals at 20° C., and about 2.9×10⁶ to3.8×10⁶ Pascals at 40° C. Representative of this class of materials isKRATON RP-6906 and RP-6912, the latter being particularly unique as alinear, multi-block copolymer having four separate blocks(styrene-ethylene/propylene-styrene-ethylene/propylene). Blends of thesematerials are also useful. This class of materials advantageouslyprovides a useful level of adhesion without adding adhesion modifiers.

Certain of the thermoplastic elastomers useful in the invention may haveinherent levels of adhesion that are either too low (especially certainhydrogenated thermoplastic elastomers) or too high (especially certainunhydrogenated thermoplastic elastomers) for maximum utility in carriertape applications. In addition, certain of the thermoplastic elastomersmay insufficiently wet the substrate surface to be bonded, may form alow quality coating, may be difficult to coat, or a combination thereof,for best utility in carrier tape applications. Accordingly, the adhesivecompositions may further and optionally comprise an adhesion modifiersuch as a tackifying resin or a liquid rubber to increase the inherentadhesion, wetting ability or coatability of the thermoplastic elastomer,or a photocrosslinking agent to decrease the inherent adhesion of thethermoplastic elastomer.

Tackifying resins can be added to the thermoplastic elastomer to enhancethe initial adhesion strength thereof and to decrease the modulusthereof so as to improve the ability of the adhesive composition toquickly wet the surface of the stored component.

Tackifying resins useful in the invention include resins derived bypolymerization of from C₅ to C₉ unsaturated hydrocarbon monomers,polyterpenes, synthetic polyterpenes, and the like. The tackifyingresins may contain ethylene unsaturation; however, saturated tackifyingresins are preferred especially for use with hydrogenated thermoplasticelastomers. Hydrocarbon tackifying resins can be prepared bypolymerization of monomers consisting primarily of olefins and diolefinsand include, for example, residual by-product monomers of the isoprenemanufacturing process. These hydrocarbon tackifying resins typicallyexhibit ball and ring softening points of from about 80° C. to 145° C.,acid numbers of from about 0 to 2, and saponification values of lessthan one. Tackifying resins useful in the invention are typically lowmolecular weight materials; e.g., a weight average molecular weight ofabout 350 to 2,500. It is also preferred that the tackifying resins becompatible with the thermoplastic elastomer, by which it is meant thatthere is no visible evidence of phase separation of these components atroom temperature.

Examples of commercially available tackifying resins useful in theinvention and which are based on a C₅ olefin fraction includeWingtack™95 and Wingtack™115 (Wingtack Plus) tackifying resins availablefrom Goodyear Tire and Rubber Co. Other hydrocarbon resins includeRegalrez™1078, Regalrez™1094 and Regalrez™1126 available from HerculesChemical Co., Inc.; Arkon resins, such as Arkon™P115, available fromArakawa Forest Chemical Industries; and Escorez™ resins available fromExxon Chemical Co. Examples of derivatives of rosin, especiallyhydrogenated derivatives, which are useful in the invention includeForal™85 and Foral™105 from Hercules Chemical Co., Inc.

Other suitable resins include terpene polymers, such as polymericresinous materials obtained by polymerization and/or copolymerization ofterpene hydrocarbons such as alicyclic, mono, and bicyclic monoterpenesand their mixtures, including carene, isomerized pinene, terpinene,terpentene, and various other terpenes. Commercially available resins ofthe terpene type include the Zonarez™ terpene B-series and 7000 seriesavailable from the Arizona Chemical Corp. Typically properties reportedfor the Zonarez™ terpene resins include ball and ring softening point ofabout 80° to 145° C., and saponification numbers of less than one.

The tackifying resin is used in an effective amount, which is an amountintended to give the appropriate level of adhesion to the componentcarried by the tape while maintaining the non-PSA character of theadhesive. The actual amount of tackifying resin employed will depend onthe level on adhesion desired, the composition of the component that isto be bonded, and the modulus of the thermoplastic elastomer. Aninsufficient amount of tackifying resin may not result in an adequateincrease in adhesion. On the other hand, the tackifying resin should notbe employed in an amount that will lead to an unacceptably high level offinal adhesion as this could make it too difficult to remove the storedcomponent from the carrier tape. In general, the minimum amount oftackifying resin needed to achieve the desired adhesion is employed,which is an amount that is typically less than 10% by weight based onthe combined weight of the tackifying resin and the thermoplasticelastomer. More preferably, about 3 to 8% by weight is used.

Alternatively, a liquid rubber may be used to increase the initialadhesion strength of the adhesive composition, decrease its modulus, andimprove its ability to wet the component carried by the tape. The liquidrubber should be selected so as to be compatible with the thermoplasticelastomer, by which is meant there is no visible evidence of phaseseparation at room temperature. The molecular weight of the liquidrubber should be selected so as to inhibit the likelihood of the liquidrubber migrating to the adhesive bond line, which could cause a weakboundary layer and premature release of the stored component. Amolecular weight of about 25,000 to 50,000 is useful. While partiallyhydrogenated liquid rubbers may be used, those which are more fullyhydrogenated are preferred, such as hydrogenated liquid isoprene rubber(e.g., Kuraray LIR 290, having a molecular weight of approximately25,000 from Kuraray Co. Ltd.).

The liquid rubber should be used in an effective amount, which is anamount that is selected by the same criteria discussed above inconjunction with the tackifying resin. Within these parameters, atypical amount of liquid rubber is less than 20% by weight, based on thecombined weight of the thermoplastic elastomer and the liquid rubber,more preferably from 5 to less than 20% by weight.

On the other hand, if the final adhesion of the thermoplastic elastomeris too high to permit easy removal of the stored component, then it maybe appropriate to add a photocrosslinking agent to decrease the finaladhesion of the thermoplastic elastomer. As used herein, a"photocrosslinking agent" refers to an agent which, upon exposure toultraviolet radiation (e.g., radiation having a wavelength of about 250to 400 nanometers), causes the thermoplastic elastomer to crosslink.

Photocrosslinking agents suitable for use in the invention includealdehydes, such as benzaldehyde, acetaldehyde, and their substitutedderivatives; ketones such as acetophenone, benzophenone and theirsubstituted derivatives such as Sandoray 1000™ (Sandoz Chemicals, Inc.);quinones such as the benzoquinones, anthraquinone and their substitutedderivatives; thioxanthones such as 2-isopropylthioxanthone and2-dodecylthioxanthone; and certain chromophore-substitutedhalomethyl-sym-triazines such as2,4-bis-(trichloromethyl)-6-(3',4'-dimethoxyphenyl)-sym-triazine,although these latter materials are less preferred because of theirpotential for generating halogen contaminants.

The photocrosslinking agent is used in a curatively effective amount, bywhich is meant an amount that is sufficient to cause crosslinking of theadhesive to provide the desired final adhesion properties to thecomponent carried by the tape. An insufficient amount ofphotocrosslinking agent may cause inadequate curing (i.e., crosslinking)of the adhesive composition such that the adhesion still remains toohigh, while excess photocrosslinking agent may result in a non-uniformcure through the bulk of the adhesive composition. Within theseparameters, the amount of photocrosslinking agent is typically about0.05 to 2% by weight of the thermoplastic elastomer, more preferablyabout 0.2 to 1% by weight, and most preferably about 0.3 to 0.5% byweight.

Minor amounts of various additives can also be included in the adhesivecompositions. Such additives include pigments, dyes, plasticizers,fillers, stabilizers, ultraviolet absorbers, antioxidants, processingoils, and the like. The amount of additives used can vary depending onthe final properties desired.

To provide enhanced utility in the handling of electronic components,the adhesive should be essentially free of ionic impurities that couldmigrate onto and contaminate the electronic component.

The adhesive composition may be readily prepared. Typically, thethermoplastic elastomer and any tackifying resin or liquid rubber aresolublized in a nonpolar organic solvent such as toluene (which may beblended with minor amounts of heptane and/or cyclohexane, or an equalparts by weight blend of methly ethyl ketone and isopropanol) using aroller mill or other low shear mixing device at room temperature forseveral hours (typically about 2 to 4 hours) until no undissolvedthermoplastic elastomer is visible. If a photocrosslinking agent isincluded it may be added at this time with additional blending on theroller mill to ensure complete dissolution. The resulting solublizedthermoplastic elastomer may be diluted to a solids content (e.g., about25%) that provides a coatable viscosity (e.g., about 4,000 to 5,000 cps)using additional nonpolar organic solvents of the type described above.A 50%/25%/25% by weight blend of toluene/methyl ethyl ketone/isopropanolis particularly preferred as a dilution solvent.

If a photocrosslinking agent has been used, the adhesive can be exposedto ultraviolet radiation having a wavelength of about 250 to 400 nm. Theradiant energy in this preferred range of wavelengths required tocrosslink the adhesive is about 100 to 1,500 millijoules/cm², morepreferably about 200 to 800 millijoules/cm².

In another embodiment, the adhesive may be provided in the form of anadhesive tape comprising a permanent backing having a layer of theadhesive thereon. By a "permanent backing" is meant a substrate orbacking layer which is intended to form an integral part of the adhesivetape rather than being a removable or releasable component, such as atemporary, protective release liner. Preferably, the permanent backingwill contain essentially no water extractable compounds or ioniccomponents so as to reduce the water sensitivity of the permanentbacking and to reduce the likelihood of the stored component becomingcontaminated by these materials.

Permanent backings useful in the invention may be provided as a singlelayer film or as a multi-layer film. The thickness of the backing mayvary widely so long as the resulting adhesive tape can be readilyhandled. Within these guidelines it is preferred that the permanentbacking have a thickness of about 12 to 50 μm, more preferably athickness of about 12 to 25 μm, and most preferably a thickness of about12 to 15 μm.

Materials from which the permanent backings useful in the invention maybe made include polyolefins (e.g., polyethylene, polypropylene,polybutene and polymethylpentene), ethylene/vinyl monomer copolymers(e.g., ethylene/(meth) acrylic acid copolymer and ethylene/vinyl acetatecopolymer), polybutadiene, poly(vinylchloride), polyurethane, polyamide,and polyester (especially polyethylene terephthalate).

Adhesive tapes useful in the invention can be easily prepared. In thisinstance, the solvated adhesive solution described previously may beapplied to the permanent backing by a variety of coating methodsincluding knife coating, slotted knife coating or reverse roll coatingand then drying at a temperature (e.g., about 65° to 120° C.) and a time(e.g., several minutes to about one hour) so as to provide the adhesivetape.

In general, the carrier tapes of the present invention are made byshaping the pockets in a sheet of polymeric material and winding thecarrier tape onto a reel to form a roll. More specifically, and withreference to the schematic view of FIG. 5 as an example, a web 200 of aflexible thermoplastic polymer is supplied as a preformed roll, as apreformed sheet, by direct extrusion (e.g., a hopper-fed, single screw,three zone extruder fitted with a sheet forming die), or by continuousinjection molding to a mold or die 204 (which may be a pair of matchedmale and female dies) that thermoform the web. Mold 204 thermoforms thepockets to the desired size and shape (allowing for any subsequentshrinkage upon cooling). The dimensions of the incoming polymeric webwill be determined by the gauge and width of the carrier tape that is tobe formed.

By "thermoforms" and "thermoforming" is meant a process that relies onthe use of both heat and pressure to deform a thermoplastic material.The heat may be provided by the mold itself, a preheater 202, or anextruder (not shown specifically). In any event, polymeric web 200 isheated sufficiently to permit thermoforming. The temperature to whichthe polymeric web must be heated varies over a broad range (i.e., about200°-370° F.) depending on the gauge and type of material that is beingthermoformed as well as the speed of the manufacturing line. The appliedpressure is sufficient to permit a high quality replication of the moldor die pattern and may be provided by, for example, the force the moldexerts upon web 200 when the mold closes or by the application of avacuum that urges the web to deform over a male die or draws the webinto a female die (i.e., vacuum thermoforming). A rotary vacuumthermoforming mold is particularly useful. Web 200 is typically cooledafter thermoforming, which can be accomplished by air cooling, fans, awater bath or a cooling oven until the thermoplastic polymer solidifies.

In general, thermoforming is a process that is familiar to those ofordinary skill in the art and is described in various references such asEncyclopedia of Polmer Science and Engineering, volume 16, secondedition, published by John Wiley & Sons, 1989, which discusses differentthermoforming processes and the use of roll-fed, sheet-fed, in-lineextrusion, and continuous web-fed systems. All of these can be employedto manufacture the carrier tapes of the invention, as can differentthermoforming tools that are described in the technical literature, suchas flat forming and rotary devices, these devices being available foruse with various thermoforming techniques such as matched mold forming,plug-assist forming, basic vacuum forming, and pressure forming.

The advancement holes are subsequently formed in a separate operationsuch as punching by punch 206.

Once the carrier tape has been prepared, the adhesive may be applied tothe bottom wall of the pockets by a variety of techniques (schematicallyillustrated in the drawings as station 207) including direct coatingonto the bottom wall, ink jet printing, and the like. If the adhesive isprovided in the form of an adhesive tape such as those described above,the tape may affixed to the bottom wall of the pocket with a layer ofadhesive (such as a high tack acrylic adhesive) or with an adhesivetransfer tape (such as #927 High Tack Adhesive Transfer Tape from 3MCompany or #9415 Double Coated Tape from 3M Company).

It is also possible to provide the adhesive as a pre-formed film thatcan be applied to the bottom wall of the pocket using equipmentconventionally employed in the labeling industry to apply a label to thebottom of a shallow, recessed pocket. In this instance, the solvatedadhesive solution described previously may be applied to a temporarysupport rather than a permanent backing but still using the techniquesdescribed above for preparing an adhesive tape. The temporary supportmay be a release liner such as a polyolefin (e.g., polyethylene orpolypropylene) or polyester (e.g., polyethylene terephthalate) film, ora paper or plastic film that has been treated with a release materialsuch as silicones, waxes, fluorocarbons, and the like. Theadhesive-coated temporary support would then be processed by the labelhandling equipment, transferring the adhesive film to the bottom wall ofthe pocket.

The carrier tape is then wound (either concentric or level windings)about the core of reel 208 to form a supply roll for storage until thecarrier tape is loaded with components. Alternatively, and as shown inFIG. 6, immediately after carrier tape 100, is formed, a componentloader 210 may fill pockets 112 with components 118, cover 120 (ifincluded) is delivered from a roll 212 and secured by an applicator 214(which is heated in the case of a cover that provides a heat-activatedbond) to the longitudinal edge surfaces of the carrier tape stripportion, and the loaded carrier tape is wound about a core or reel 216for storage or delivery. Carrier tape 100 is advanced by sprockets 209and 211.

In use, the carrier tape is unloaded as shown in the schematic exampleof FIG. 7, which illustrates a carrier tape 100 in combination with arobotic placement machine 218. Supply reel 216 provides carrier tape100. A stripper assembly 220 peels cover 120 (if included) from carriertape 100 around a stripper block 222, which assists in preventing thestripper assembly from pulling the carrier tape away from its designatedpath. Carder tape 100 is advanced by a sprocket 224, to move the carriertape toward robotic placement machine 218. As each successive componentreaches the desired pick-up point, the robotic placement machine graspsthe component (either manually or by suction) and places it, forexample, on a circuit board in the appropriate location. Preferably,adhesive 119 does not transfer to component 118 upon removal from thecarrier tape, by which it is meant that to the unaided human eye thereis no visible adhesive residue on the component.

The carrier tapes of the invention are particularly useful in theelectronics industry for transporting and delivering surface mountelectronic components such as memory chips, integrated circuit chips,resistors, connectors, dual in-line processors, capacitors, gate arrays,etc. However, the carrier tapes may be used to transport othercomponents such as small springs, clips, and the like.

The present invention has now been described with reference to severalembodiments thereof. It will be apparent to those skilled in the artthat many changes can be made in the embodiments described withoutdeparting from the scope of the invention. Hence, the scope of thepresent invention shall not be limited by the structures describedherein, but only by structures described by the language of the claimsand the equivalents of those structures.

The embodiments for which an exclusive property or privilege is claimedare defined as follows:
 1. A flexible carrier tape for storage anddelivery of components by an advancement mechanism, the carrier tapecomprising:(a) a strip portion having a top surface, a bottom surfaceopposite the top surface; (b) a plurality of aligned pockets forcarrying the components, the pockets being spaced along the stripportion and opening through the top surface thereof, wherein each pocketcomprises:(i) at least one side wall adjoining and extending downwardlyfrom the strip portion; and (ii) a bottom wall adjoining the at leastone side wall to form the pocket; and (c) a non-pressure sensitiveadhesive comprising a thermoplastic elastomer block copolymer on thebottom wall of the pocket for retaining a component in the pocket,wherein the adhesive has a storage modulus at room temperature that isgreater than 3×10⁵ Pascals.
 2. A flexible carrier tape according toclaim 1 wherein each pocket comprises:(i) four side walls each atgenerally right angles with respect to each adjacent side wall, the sidewalls adjoining and extending downwardly from the strip portion; and(ii) a bottom wall adjoining the side walls to form the pocket.
 3. Aflexible carrier tape according to claim 1 wherein the bottom wall ofeach pocket includes an aperture formed through the bottom wall.
 4. Aflexible cartier tape according to claim 1 wherein each of the pocketsis essentially identical and are equally spaced along the strip portion.5. A flexible carrier tape according to claim 1 wherein the plurality ofpockets includes more than one aligned column of pockets extending alongthe length of the strip portion.
 6. A flexible carrier tape according toclaim 1 wherein the ship portion has first and second parallellongitudinal edge surfaces and at least one of the edge surfacesincludes a plurality of equally spaced holes for receiving theadvancement mechanism.
 7. A flexible carrier tape according to claim 1wherein the adhesive has a storage moduls greater than 1×10⁶ Pascals. 8.A flexible carrier tape according to claim 1 wherein the thermoplasticelastomer block copolymer comprises repeating blocks of styrene andrepeating blocks of a rubbery elastomer.
 9. A flexible carrier tapeaccording to claim 1 wherein the thermoplastic elastomer block copolymeris selected from the group consisting ofstyrene-ethylene/propylene-styrene block copolymer,styrene-ethylene/propylene-styrene-ethylene/propylene block copolymer,styrene-ethylene/butylene-styrene block copolymer, and blends thereof.10. A flexible carrier tape according to claim 1 wherein the adhesivefurther comprises a tackifying resin.
 11. A flexible carrier tapeaccording to claim 10 wherein the tackifying resin is present in anamount of less than 10% by weight, based on the combined weight of thethermoplastic elastomer block copolymer and tackifying resin.
 12. Aflexible carrier tape according to claim 1 wherein the adhesive furthercomprises a liquid rubber.
 13. A flexible carrier tape according toclaim 12 wherein the liquid rubber is present in an amount of less than20% by weight based on the combined weight of the thermoplasticelastomer block copolymer and the liquid rubber.
 14. A flexible carriertape according to claim 1 wherein the adhesive further comprises aphotocrosslinking agent.
 15. A flexible carrier tape according to claim1 wherein at least one of the pockets contains a surface mountelectronic component.
 16. A flexible carrier tape according to claim 1further including a cover releasably secured to the top surface of thestrip portion, extending along the strip portion, and covering theplurality of pockets.
 17. A flexible carrier tape according to claim 1wound about the core of a reel.
 18. A flexible carrier tape according toclaim 1 wherein the adhesive exhibits a peel adhesion of about 20 to 200grams per linear inch width to the component.
 19. A flexible carriertape according to claim 18 wherein the adhesive exhibits a peel adhesionof about 50 to 140 grams per linear inch width to the component.
 20. Aflexible carrier tape according to claim 18 wherein the adhesiveexhibits a peel adhesion of about 20 to 200 grams per linear inch widthafter dwelling in contact with the component for a period of at least 7days under ambient conditions.
 21. A flexible carrier tape according toclaim 1 wherein the component can be removed from the pocket without theadhesive transferring to the component.
 22. A flexible carrier tape forstorage and delivery of electronic components by an advancementmechanism, the carrier tape comprising:(a) a strip portion having a topsurface, a bottom surface opposite the top surface, and first and secondparallel longitudinal edge surfaces, at least one of the edge surfaceshaving a plurality of equally spaced through holes for receiving theadvancement mechanism; and (b) a plurality of aligned pockets forcarrying the electronic components, the pockets being equally spacedalong the strip portion and opening through the top surface thereof,each pocket comprising(i) four side walls each at generally right angleswith respect to each adjacent side wall, the side walls adjoining andextending downwardly from the strip portion; and (ii) a bottom walladjoining the side walls to form the pocket; and (c) a non-pressuresensitive adhesive on the bottom wall of the pocket, wherein theadhesive has a storage modtfius at room temperature that is greater than3×10⁵ Pascals and inherently displays sufficient adhesion to thecomponent at room temperature to retain the component in the pocket. 23.A flexible carrier tape according to claim 22 wherein the adhesivecomprises a thermoplastic elastomer block copolymer.
 24. A flexiblecarrier tape according to claim 23 wherein the thermoplastic elastomerblock copolymer is selected from the group consisting ofstyrene-ethylene/propylene-styrene block copolymer,styrene-ethylene/propylene-styrene-ethylene/propylene block copolymer,styrene-ethylene/butylene-styrene block copolymer, and blends thereof.25. A flexible carrier tape according to claim 22 wherein the adhesiveexhibits a peel adhesion of about 20 to 200 grams per linear inch widthto the component but does not transfer to the component when thecomponent is removed from the pocket.
 26. A flexible carrier tapeaccording to claim 22 wherein at least one of the pockets contains anelectronic component.
 27. A flexible carrier tape according to claim 1wherein the non-pressure sensitive adhesive is in the form of anadhesive tape comprising a permanent backing with a layer of thenon-pressure sensitive adhesive on the permanent backing, the permanentbacking being disposed between the bottom wall of the pocket and thelayer of the non-pressure sensitive adhesive.
 28. A flexible carriertape according to claim 27 wherein the adhesive tape is affixed to thebottom wall of the pocket by a layer of an adhesive or by a secondadhesive tape.
 29. A flexible carrier tape according to claim 22 whereinthe non-pressure sensitive adhesive is in the form of an adhesive tapecomprising a permanent backing with a layer of the non-pressuresensitive adhesive on the permanent backing, the permanent backing beingdisposed between the bottom wall of the pocket and the layer of thenon-pressure sensitive adhesive.
 30. A flexible carrier tape accordingto claim 29 wherein the adhesive tape is affixed to the bottom wall ofthe pocket by a layer of an adhesive or by a second adhesive tape.